This invention relates to the actuators or buttons applied to the aerosol valve stems of aerosol packages in particular.
The science and technology of such packages and their components are described by the text "Aerosols: Science and Technology", published by Interscience Publishers, Inc., New York, copyrighted 1961, the entire contents of this text being hereby incorporated by this reference into the present application.
The prior art has recognized that such actuators involve the problem of clogging and has made various attempts at solving this problem as exemplified by the following U.S. patents
McKernan Pat. No. 3,250,474, dated May 10, 1966 PA1 Barker Pat. No. 3,378,205, dated Apr. 16, 1968 PA1 Venus, Jr. Pat. No. 3,427,270, dated Apr. 8, 1969 PA1 Lewiecki et al. Pat. No. 3,428,223, dated Feb. 18, 1969 PA1 Beard Pat. No. 3,545,682, dated Dec. 8, 1970 PA1 Grothoff Pat. No. 3,602,407, dated Aug. 31, 1971
None of the constructions of the above patents have ever been applied to commercial aerosol packages, insofar as is known. They all have inherent disadvantages.
One disadvantage is that when any such actuator receives the pressurized product from the aerosol valve stem of an aerosol package, unsealing its orifice, the pressure drop occurring within the actuator adjacent to the actuator's orifice, causes the orifice to become resealed, this action occurring repeatedly with great rapidity to produce a chattering action. This follows from the fact that all anti-clogging or self-sealing actuators rely on the pressure of the product for unsealing, this pressure acting against a piston area provided in one way or another, and against some form of elastic means normally biasing the valve arrangement involved to a normally closed position sealing the actuator's orifice so that product trapped within the actuator is sealed against the atmosphere which might otherwise solidify the product within the actuator.
Such actuators are necessarily very small in dimensions and another disadvantage has been that the prior art actuators have involved parts which cannot be easily injection molded as plastic parts capable of assembly by mass production methods, keeping in mind the very large quantities of aerosol packages involved by the production of any one kind of package.
Even conventional actuators which do involve the clogging problem and which are of one-piece construction and capable of being injection molded in the large quantities required, have the disadvantage, shared by the non-clogging actuator proposals, that the discharge rate is unvariably fixed by the discharge orifice diameter. In many instances, it would be desirable to be able to vary the discharge rate and spray characteristics of an aerosol package, under control by the user of the package.
A non-clogging aerosol valve stem actuator, sometimes called a button, which is free from the disadvantages described above, is disclosed and claimed in the U.S. Laauwe patent application Ser. No. 490,077, filed July 19, 1974, on which U.S. Pat. No. 3,913,804, issued Oct. 21, 1975.
That application discloses an aerosol valve stem actuator comprising a substantially rigid plastic body having a hole formed upwardly therein for receiving the stem and a passage formed through the body transversely with respect to the stem hole and into which that hole opens. The body forms a front end wall closing the adjacent or front end of the passage, this front end wall having a discharge orifice formed through it, the passage having a back end portion forming a cylinder which contains a substantially rigid slidable plastic reciprocating piston positioned in the cylinder and having a piston rod extending forwardly with a front end engaging the body's front end wall around the orifice and normally closing the orifice when the piston is at an advanced position and separating from the front end wall, to unseal the orifice, when the piston is at retracted positions.
The body has an external back end surface surrounding the back end of the cylinder and having screw threads, a product discharge governor formed by a cap having a side wall with internal screw threads being screwed on the screw threads of this surface. This cap has an internal abutment surface engaged by the piston when in its retracted position and adjustably fixing this position dependent on the position of the cap. A coil compression spring connects with the inside of said cap and extends forwardly and connects to the piston to bias the piston to its advanced position with its piston rod front end engaging the body's front end wall around the orifice and normally closing and sealing the orifice.
The actuator's piston and piston rod form a piston area facing the body's front end, and having a flow rate capacity at the pressure and constituancy of the product, relatively proportioned to maintain the pressure applied to the piston at a value holding the piston at its retracted position continuously as long as the product flows through the passage and through the dispensing orifice. The valve stem hole opens transversely into the body's passage at a location spaced far enough backwardly from the orifice and towards the piston for the latter to be continuously forced to its retracted position constantly during maintenance of the product flow.
The front end of the piston rod and the inside of the body's front end wall respectively have male and female slidingly interfitting elements, such as vanes or baffles, contoured substantially as curved segments to form a swirl chamber, the side edges of these segments being interspaced to form side orifices or openings when the piston rod is retracted more or less, depending on the governor. The piston rod and the inside of the surface of the body's passage have slidably interfitting guide elements holding the piston rod and piston against rotation when the governor is screwed rotatively to govern the product discharge.
All of the parts of the above described earlier Laauwe actuator are made of substantially rigid plastic, excepting for the possible use of a metal spring to bias the actuator to its normally closed position. Prototypes of that actuator have been made by using plastic injection molding techniques to form the plastic parts. The reciprocating piston and the cylinder in which it reciprocates can be made to interfit adequately to avoid appreciable leakage between the piston and the cylindrical wall, when the actuator is used. The production of the prototype has proven that the necessary interfitting can be accomplished under commercial large-quantity production conditions.